This invention relates in general to web drive mechanisms and in particular to a ribbon drive mechanism for ink ribbons employed in a ribbon cartridge in serial printer applications.
Although the invention is applicable to various web, tape, strand and ribbon-like materials, it has been found particularly useful in the environment of ink ribbons as used in serial printers. Therefore, without limiting the meaning of the word "ribbon", the invention will be described in this environment.
In devices in which any web material is to be delivered or transferred from a rotatable reel, drum, spool, spindle or a like receptacle to another similar and compatible receptacle, it is normally necessary to provide a web drive means by which force is applied to the web material to remove it from the receptacle providing the supply of web material. Also, normally a web tension means is provided for maintaining a certain amount of tension in the web material during its transfer. Tension in the web material during the transfer is desired for economic reasons and user acceptance so that a greater amount of web material may be placed on each receptacle and so the web material will be tightly wound on the receiving receptacle and will not fall therefrom during handling. In addition, web take-up drive means for the take-up receptacle is required to provide the force necessary to place the web material on the receiving receptacle upon its deliverance from the supply receptacle. In some instances, the web drive means and the web take-up drive means comprises a single means, which performs both functions.
In the particular environment of ink ribbons employed in ribbon cartridges in serial printers, a certain amount of tension in the ribbon is required for proper ribbon feed and ribbon location at the printing position to assure acceptable print quality of the printed material. Ribbon drive means provides the force to move the ribbon the desired amount between successive print operations. The amount of ribbon movement is dependent upon the particular pitch and type of ribbon being used.
It is well known in the art to provide a drive roller with pointed projections thereon in conjunction with spring means for applying the ribbon drive force to the outer periphery of the ribbon wound on the take-up spool as disclosed in U.S. Pat. No. 3,604,549. It is also known to provide a pawl and ratchet arrangement for rotating the spindles, which rotatably support the ribbon supply spool and the ribbon take-up spool as disclosed in U.S. Pat. No. 3,346,090. In U.S. Pat. No. 3,528,536, a drive roller and a friction or pressure roller in conjunction with spring means is disclosed to provide the ribbon drive force.
Such prior art solutions have utilized complex mechanical means in conjunction with spring means to provide the necessary control of the drive means to transfer the web or ribbon material from the supply spool to the take-up spool.
With the prior art in mind, it is an object of the present invention to provide an improved ribbon drive means, which is compatible with cartridges of the present type.
Another object of this invention is to provide a cost effective ribbon drive means for ink ribbons contained in cartridges along the presently described vane.
Other objects and advantages of this invention will be evident from the specification and claims in conjunction with the accompanying drawing illustrative of the invention.